Re: Nil items in NSMutableSet
Re: Nil items in NSMutableSet
- Subject: Re: Nil items in NSMutableSet
- From: Daniel DeCovnick <email@hidden>
- Date: Tue, 16 Mar 2010 15:34:17 -0700
There was a thread on this list a few days ago about effective method
swizzling into Apple classes. Despite being replete with warnings
about "Don't use it in production code," it IS doable, and very, very
cool, IMHO.
-Dan
On Mar 16, 2010, at 2:18 PM, Alejandro Rodriguez wrote:
You were right, my equality is not transitive.
id ob = [[objectClass alloc] initWithId:@"hello"];
[ob isEqual:@"hello"]; //returns YES
[@"hello" isEqual:ob]; //returns NO
That may very well be the problem... now... I have no idea on how I
will make the second test return YES.
doesn't that depend on the implementation of isEqual of the asking
object in this case NSString? Have any of you had to deal with this
before? I'll dive into the docs and see what details I find that
might be useful.
Seems we are getting somewhere
cheers!
Alejandro
On Mar 16, 2010, at 2:45 PM, Clark Cox wrote:
On Tue, Mar 16, 2010 at 11:35 AM, Thomas Davie
<email@hidden> wrote:
Your code doesn't account for the possibility that the order of
comparison might happen in the other order (i.e. [@"123" isEqual:
object]). I wouldn't be surprised if NSSet is assuming that
equality
is transitive (i.e. [a isEqual: b] == [b isEqual: a]).
For reference, this property is not transitivity, the transitivity
relation is:
a -> b ^ b -> c => a -> c (for some relation ->)
The one you're looking for is commutativity.
Indeed; must have been echos of my previous life as a C++ programmer
creeping into the Obj-C part of my brain (in C++, the std::set class
uses less than, instead of equality, where transitivity is the
important property, not commutativity).
:)
--
Clark S. Cox III
email@hidden
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